Gland packing and sealing apparatus comprising it

ABSTRACT

To provide a novel gland packing and a sealing apparatus comprising this, wherein the gland packing displays high and stable sealability for a stem and an inner wall surface of a stuffing box even for uses further requesting the movability (rotation and reciprocating movement), and further, gives excellent effects, such as decrease of moving resistance of a stem, shape stability, adaptability to a corroded and worn-out stem and stuffing box, function for receiving shafts, easiness of equipment, simplification of sealing structure, and compactness of a sealing apparatus. The gland packing, according to the present invention, is a ring packing of which the cross sectional shape is a quadrilateral, wherein both two edges at inner and outer diameter sides of the quadrilateral are parallel to a central axis of the gland packing, and wherein the other two edges have slopes of the same orientation as to an axis perpendicular to the central axis, with the gland packing being characterized in that an inner-diameter-side acute angle portion and an outer-diameter-side acute angle portion of the quadrilateral are made flat portions.

TECHNICAL FIELD

The present invention relates to a gland packing and a sealing apparatuscomprising this.

Particularly, the present invention relates to a gland packing and asealing apparatus comprising this, wherein the gland packing is, forexample, equipped in a stuffing box and can effectively seal such as astem in this stuffing box.

More particularly, the present invention relates to a gland packing anda sealing apparatus comprising this, wherein the gland packing can sealmoving portions of such as rotary pumps, valves, stirrers, andreciprocating pumps, and is effective when it is utilized in order tofit for various moving properties and all the sealing requisiteproperties of such as a stem.

BACKGROUND ART

As to a gland packing which is equipped in a stuffing box and whichseals such as a stem in the stuffing box and inner wall surfaces of thestuffing box, hitherto, the cross sectional shape thereof has in generalbeen a rectangle (square or oblong), a parallelogram, or a trapezoidhaving a right angle, and it has been generally known that at least anytwo of the gland packings are mutually attached closely, piled, and thenused.

However, conventional gland packings have various problems. For example,when at least two gland packings of which all the cross sectional shapesare rectangles above are piled and equipped to a stem, there areproblems such that: there is much scatter of the extension anddeformation of the gland packings in the vertical directions(hereinafter, referred to as “in the directions of the inner and outerdiameters”) to the tightening face pressure of the packing holder; andthe exceedingly tightened portions and the loosely tightened portionseasily coexist. Therefore, the tightening face pressure of the packingholder is inevitably increased exceedingly. Therewith, there is ademerit of increasing the moving resistance and required torque of thestem, or there is a fault such that: the gland packing materials arethrust into an opening at the stem side, and then protruded; andtherefore the lowering of the sealing performance (sealability) and theleakage of enclosed materials are caused.

Accordingly, an attempt to facilitate the extension and deformation ofthe gland packing and to lower the tightening face pressure of thepacking holder is made by comparatively lowering the density of thegland packing as used (namely, softening the gland packing). However,because of the character such that the extension and deformation amountin the directions of the inner and outer diameters of the aforementionedlow-density gland packing is smaller than the compression anddeformation amount in the direction of tightening the packing holder, itwas necessary to further increase the tightening face pressure of thepacking holder finally so that the stem would be sealed sufficiently.Furthermore, because the strain ratio (strain amount) of theaforementioned low-density gland packing is large, the number of glandpackings necessary for sealing the stem may exceed an acceptable limitin the stuffing box, and besides there is a demerit of not achieving thefunction as a shaft receiver that prevents a moving error or vibrationof the stem due to its softness, and there is also a problem of thepermeation and leakage of the material itself because of the lowdensity.

On the other hand, if the density is made high, the shape stability ofthe gland packing is improved, and the gland packing can be madeexcellent in such as functions as the shaft receiver. However, theextension and deformation amount in the directions of the inner andouter diameters to the tightening face pressure of the packing holder isfundamentally small. Therefore, it is necessary to further increase thetightening face pressure of the packing holder so that the stem would besealed sufficiently. Therewith, caused are problems such that thesealing apparatus is enlarged and the handling convenience is lost.

As to the sealing apparatus, in addition to those which have a structurein which main packings of a kind are used in the above way, sealingapparatuses for such as stems in which at least two kinds of glandpackings comprised of different materials or having different propertiesare mutually attached and equipped in a stuffing box have been wellknown hitherto. However, the reason that such a structure is selected isthat at least two requisite or deficient performances (e.g. sealability,heat resistance, pressure resistance, and frictional resistance) aresatisfied at a stroke. This was impossible for conventional glandpackings of a kind alone. Therefore, in view of easiness andsimplification of the sealing apparatus, there are problems such that atleast two kinds of gland packings inevitably cannot help being equippedas the main packings.

In addition, U.S. Pat. No. 4,328,974 discloses a sealing apparatus so asto have a stress concentration in directions of the inner and outerdiameters of a packing, in which a low-density gland packing of whichthe cross sectional shape is a parallelogram is placed betweenhigh-density gland packings of which the cross sectional shapes aretrapezoids, and the shapes of both are made not to be mutually attached,and besides they are piled and equipped on a stem in a stuffing box, andthereafter the packings are mutually attached by tightening a packingholder. However, in the sealing apparatus according to this priorinvention, there are various problems such that: 1) it is necessary tocombine at least two packings having different densities; 2) low-densitypackings having a large strain ratio account for majority; 3) there is astress concentration, but the number thereof is small; 4) in other thanthe stress concentration, the tightening face pressure of the packing isnot transmitted more than that of a rectangular packing; and 5) thefunction of the low-density packing portion as a shaft receiver islowered.

DISCLOSURE OF THE INVENTION

Object of the Invention

Accordingly, an object of the present invention is to provide a novelgland packing and a sealing apparatus comprising this, wherein the glandpacking displays high and stable sealability for a stem and an innerwall surface of a stuffing box even for uses further requesting themovability (rotation and reciprocating movement), and further, givesexcellent effects, such as decrease of moving resistance of a stem,shape stability, adaptability to a corroded and worn-out stem andstuffing box, function for receiving shafts, easiness of equipment,simplification of sealing structure, and compactness of a sealingapparatus.

SUMMARY OF THE INVENTION

The present inventor diligently studied to solve the above-mentionedproblems, and focused upon what improvement that has never been foundshould be carried out as to the shape of the gland packing for thepurpose of enabling it to display high sealability, and then repeatedvarious presumptions and experiments. The reason therefor is as follows.In the past, as is mentioned above, there were examples in which theshapes were slightly thought out. However, even in those cases,substantially expected are the effects as obtained by focusing upon thecombinations of materials or properties of gland packings themselves,and as a result, by that alone, a definite effect can be obtained,whereas various demerits are also caused. That is to say, he thoughtthat the desirable effects of which the improvement has hitherto beenattempted by contriving the properties should be intended to be given bycarrying out a characteristic improvement mainly on the shape of thegland packing.

Based on the above findings, he repeated trials and errors, and variousstudies. As a result, he has completed the present invention byconfirming that a novel gland packing and a sealing apparatus comprisingthis can solve the above-mentioned problems at a stroke; which glandpacking is a so-called conical-plate-shaped gland packing, in which thecross sectional shape of the ring portion of the ring packing is aquadrilateral, and this quadrilateral consists of twoinner-diameter-side and outer-diameter-side edges parallel to a centralaxis of the gland packing, and the other two edges facing each other andhaving slopes of the same orientation as to an axis perpendicular to thecentral axis, wherein portions corresponding to upper and lower ends inthe direction of the central axis, namely, an inner-diameter-side acuteangle portion and an outer-diameter-side acute angle portion of thegland packing, are made flat portions.

When a load is applied in the upward and downward directions of thecentral axis, the gland packing, according to the present invention, isefficiently deformed in the directions of the inner and outer diametersas if an umbrella were spread (so-called washer deformation of conicalplate diameter), so that a stress is caused. Therefore, for example,when this gland packing is equipped to a stem in a stuffing box and thentightened, such as greatly excellent sealability can be displayed evenif the tightening load is either equal to or less than the conventionaltightening load. In addition, when the above equipment is carried out,at least two gland packings are usually used similarly to theconventional equipment. In addition to being characterized in that thegland packing according to the present invention isconical-plate-shaped, as is mentioned above, the flat portions arearranged at the upper and lower ends. Therefore, the gland packings cancontact with each other more certainly and stably than gland packingshaving no flat portions. The flat portions contact with each otherusually when the equipment is carried out in such a manner that theslope orientation (shape) of one gland packing is opposite to that ofits neighboring gland packing in reference to the direction of thecentral axis. For example, if this relation is repeated by at least twogland packings, then the equipment is carried out in such a manner thatthe slopes are alternately oriented as a whole. As a result, as to thesealing apparatus in which the present invention gland packing ispractically used, very efficient and high sealability can be displayedmultistagewise both to the inner and outer diameter sides almost withoutdepending upon the distance from the tightening portion, because of theabove certain and stable contact and of the so-called alternatingequipment.

That is to say, a gland packing, according to the present invention, isa ring packing of which the cross sectional shape is a quadrilateral,wherein both two edges at inner and outer diameter sides of thequadrilateral are parallel to a central axis of the gland packing, andwherein the other two edges have slopes of the same orientation as to anaxis perpendicular to the central axis,

with the gland packing being characterized in that aninner-diameter-side acute angle portion and an outer-diameter-side acuteangle portion of the quadrilateral are made flat portions.

In addition, a sealing apparatus, according to the present invention, isequipped with gland packings that are piled in a stuffing box, and sealsthe stuffing box,

with the sealing apparatus being characterized in that:

each of the gland packings is a gland packing in which flat portions arearranged at an inner-diameter-side acute angle portion and anouter-diameter-side acute angle portion of a ring packing of which thecross sectional shape is a quadrilateral including: two edges at innerand outer diameter sides of the quadrilateral wherein the two edges areparallel to a central axis of the gland packing; and the other two edgeswhich have slopes of the same orientation as to a vertical axisperpendicular to the central axis; and

at least one of the gland packings as equipped in the stuffing box isequipped therein in such a manner that the orientations of the slopes ofthe other two edges of the at least one of the gland packings aredifferent from those of the other gland packings.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1( a) is a perspective view showing one working example of thepresent invention gland packing. FIG. 1( b) is a perspective view whenthe gland packing as shown in FIG. 1( a) is upside down. In addition,FIG. 1( c) is a projective view in the width direction of the glandpacking as shown in FIG. 1( a) or (b), and FIG. 1( d) is a projectiveview in the thickness direction of the gland packing as shown in FIG. 1(a) or (b).

Both FIGS. 2( a) and (b) are partially cross sectional views showing oneworking example of the present invention gland packing when the glandpacking is cut by a plane including a central axis 2 a. Then, FIG. 2( a)represents the case of α>β, and FIG. 2( b) represents the case of α<β.

FIG. 3 is a partially cross sectional view showing a gland packing as areferential art when the gland packing is cut by a plane including acentral axis 2 a.

Both FIGS. 4( a) and (b) are partially end sectional views showing oneworking example of the present invention gland packing when the glandpacking is cut by a plane including a central axis 2 a. Then, FIG. 4( a)represents the gland packing before deformation, and FIG. 4( b)represents the gland packing after deformation.

FIG. 5 is a schematic cross sectional view showing one working exampleof a sealing apparatus comprising the present invention gland packing.FIG. 5( a) represents the sealing apparatus before sealing (before apacking holder 8 is tightened), and FIG. 5( b) represents the sealingapparatus after sealing (after a packing holder 8 is tightened).

FIG. 6 is a schematic cross sectional view showing one working exampleof a sealing apparatus comprising the present invention gland packing.FIG. 6( a) represents the sealing apparatus before sealing (before apacking holder 8 is tightened), and FIG. 6( b) represents the sealingapparatus after sealing (after a packing holder 8 is tightened).

FIG. 7 is a schematic cross sectional view showing one working exampleof a sealing apparatus comprising the present invention gland packingand further being equipped with an adaptor packing, and represents thesealing apparatus before sealing (before a packing holder 8 istightened).

FIG. 8 is a schematic cross sectional view showing one working exampleof a sealing apparatus comprising the present invention gland packingand further being equipped with an adaptor packing, and represents thesealing apparatus before sealing (before a packing holder 8 istightened).

FIG. 9 is a schematic cross sectional view showing one working exampleof a sealing apparatus being equipped with a combination of the presentinvention gland packing and a conventional-type gland packing, andrepresents the sealing apparatus before sealing (before a packing holder8 is tightened).

FIG. 10 is a schematic cross sectional view showing one working exampleof a sealing apparatus being equipped with a combination of the presentinvention gland packing and a conventional-type gland packing, andrepresents the sealing apparatus before sealing (before a packing holder8 is tightened).

FIG. 11 is a schematic cross sectional view showing one working exampleof a sealing apparatus being equipped with a combination of the presentinvention gland packing and a conventional-type gland packing, andrepresents the sealing apparatus before sealing (before a packing holder8 is tightened).

FIG. 12 is a schematic cross sectional view showing one working exampleof a sealing apparatus comprising the present invention gland packingand further being equipped with an adaptor packing and a hard ring, andrepresents the sealing apparatus before sealing (before a packing holder8 is tightened).

Both FIGS. 13( a) and (b) are partially end sectional views showing oneworking example of the present invention gland packing when the glandpacking is cut by a plane including a central axis 2 a, wherein thestructure of the present invention gland packing is partially deformed.

FIG. 14 is a graph in which the X axis represents a “length distance”from the pressurizing face of a packing holder, and in which the Y axisis an “inner-diameter-side transmitted face pressure (MPa)”corresponding to this length distance.

FIG. 15 is a graph in which the X axis represents a “length distance”from the pressurizing face of a packing holder, and in which the Y axisis an “outer-diameter-side transmitted face pressure (MPa)”corresponding to this length distance.

FIG. 16 is a schematic cross sectional view showing one example of asealing apparatus for testing sealability of a gland packing(sealability-testing apparatus) as mentioned in the Examples.

[Explanation of the Symbols]  1 Gland packing  2a Central axis  2bVertical axis to central axis  2c Diametric axis  3a Inner-diameter-sideflat portion  3b Inner-diameter-side obtuse angle portion  4aOuter-diameter-side obtuse angle portion  4b Outer-diameter-side flatportion  3a′ Inner-diameter-side acute angle portion  4b′Outer-diameter-side acute angle portion  3c Inner-diameter-sidestress-concentrated point  4c Outer-diameter-side stress-concentratedpoint  5 Stem  6 Stuffing box  7 Inner bottom portion of stuffing box  8Packing holder  8a Pressurizing face of packing holder  9 Tighteningbolt 10 Adaptor packing 10a Gland packing of which the cross sectionalshape is rectangular 10b Hard ring 11 O-ring 12 Tightening bolt 13Pressurizing opening 14 Bearings 15 Stem (driving shaft) 16Gas-enclosing portion 17 Thrust bearings 18 Portion equipped with torquewrench

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, the details of the present invention gland packing andsealing apparatus comprising this are specifically explained.

As is shown in FIGS. 1( a) and (b), the shape of the gland packingaccording to the present invention (which may hereinafter be referred toas the present invention gland packing) is a ring packing similarly togeneral gland packings.

The present invention gland packing is a gland packing in which portionscorresponding to the inner-diameter-side acute angle portion and theouter-diameter-side acute angle portion of the gland packing of whichthe cross sectional shape of the ring portion in the central axisdirection (namely the cross sectional shape as cut by a plane includingthe central axis) is a quadrilateral, namely, a portion corresponding tothe upper end and a portion corresponding to the lower end in view of adirectional axis along the central axis, are made flat portions.

Herein, the above quadrilateral is like the cross section of the glandpacking as shown in FIG. 3, and is a quadrilateral in which both aninner-diameter-side edge 1 c and an outer-diameter-side edge 1 d areparallel to a central axis 2 a, and in which the other two edges 1 a and1 b have slopes of the same orientation as to a vertical axis 2 bperpendicular to the aforementioned central axis 2 a. As is shown inFIG. 3, the above slope means an angle α or an angle β. The angle α isan angle between the vertical axis 2 b and the edge 1 a, and the angle βis an angle between the vertical axis 2 b and the edge 1 b. Furthermore,the above slopes of the same orientation are defined as that thespreading of the above angles are of the same orientation when the edge1 a and the edge 1 b cross the vertical axis 2 b at their respectiveangles on the assumption that the vertical axis 2 b is regarded as thestandard and that these angles are defined as 0° when the edge 1 a andthe edge 1 b overlap with the vertical axis 2 b. Incidentally, the glandpacking as shown in FIG. 3 is a gland packing as a referential art forexplaining the characteristics of the present invention gland packing.

In addition, the above inner-diameter-side acute angle portion andouter-diameter-side acute angle portion, like the portion 3 a′ and theportion 4 b′ as shown in FIG. 3 respectively, mean two angle portionshaving an acute angle among interior angles of the above quadrilateral.The present invention gland packing is a gland packing, in which theseportion 3 a′ and portion 4 b′ are made flat portions as mentioned below.

As to the above flat portions, namely, the flat portions that thepresent invention gland packing, has, it is enough that, for example,those portions are flat to such an extent that the gland packing cansubstantially stably and certainly contact with a flat portion of suchas a neighboring gland packing or an adapter packing when the glandpacking is actually equipped to such as a sealing apparatus and thenused. There is no especial limitation thereto. Therefore, the above flatportions don't need to be perfect plane portions to overlap with a planeperpendicular to the central axis. The flat portions may have a slightslope, or may have a portion partially having a curved surface, or mayhave different cross sectional shapes depending upon the position of thecross section (depending upon of which portion the cross section isobserved). When the above flat portions are shown as an optional crosssectional shape of the ring portion (an optional cross sectional shapeas cut by a plane including the central axis 2 a), specifically,preferred examples thereof include a shape such as the portion 3 a andthe portion 4 b that are shown in FIGS. 2( a) and (b). When the totalwidth in the vertical axis 2 b direction as to the ring portion of thegland packing is regarded as t, the respective widths A and B of theflat portions 3 a and 4 b in the direction of the vertical axis 2 b arefavorably A<0.5 t and B<0.5 t, more favorably A<0.3 t and B<0.3 t. Inthe case where the above widths A and B are more than 0.5 t, there is apossibility that the gland packing cannot efficiently be deformed in thedirections of the inner and outer diameters (so-called washerdeformation of conical plate) by a load applied from the central axisdirection, resulting in lowering the sealability, because the stress isnot sufficiently caused in the directions of the inner and outerdiameters.

In the present invention gland packing, there is no especial limitationon the range which the angles α and β as shown in FIGS. 2( a) and (b)can take. Specifically, they are favorably 0°<α<90° and 0°<β<90°, morefavorably 5°<α<40° and 0°<β<40°. However, they may fitly be set inconsideration of the length A of the above flat portion. In general, ifthe widths A and B of the flat portions are wide, there are many caseswhere the angles α and β are set on the large side. Or otherwise if thewidths A and B of the flat portions are narrow, there are many caseswhere the angles α and β are set on the small side. In addition, theangle α may be either equal to the angle β (α=β) or different from theangle β (α≠β), and there is no especial limitation thereto. However, α=βis generally favorable in respect to such as having wide use.Furthermore, the angle difference between the angle α and the angle β,is favorably 0≦|α−β|<20°.

When the angles α and β are within the above ranges and further theangle difference between the angle α and the angle β (|α−β|) is in theabove-mentioned range, it can be prevented that the clearances as formedbetween the gland packings are too large, and that the deformationamount (strain amount) necessary for sufficiently displaying thesealability is excessively large. At the same time, the malfunction ofthe equipability and handling ability can be prevented wherein the causeof the malfunction is that the total initial equipping length of thegland packings as equipped is too long.

There is no especial limitation on the cross sectional shape of thepresent invention gland packing if the above flat portions 3 a and 4 b,and angle α and angle β satisfy the above-mentioned conditions.Specifically, examples thereof include: (1) the two edges at the innerand outer diameter sides have the same length, namely, α=β; (2) of thetwo edges at the inner diameter side 1 c and the outer diameter side 1d, the edge at the outer diameter side 1 d is longer, namely, α>β (FIG.2( a)); and (3) of the two edges at the inner diameter side 1 c and theouter diameter side 1 d, the edge at the inner diameter side 1 c islonger, namely, α<β (FIG. 2( b)).

In the cross sectional shape of the present invention gland packing,there is no especial limitation on its inner and outer diameters or thesizes of such as the inner-diameter-side edge 1 c and theouter-diameter-side edge 1 d, and it is enough that they are in suchranges as to hold as a ring packing in which the flat portions and theangles α and β can satisfy the above conditions, particularly as a glandpacking.

The present invention packing has the above-mentioned characteristicform. Therefore, for example, in the case where the stem 5 in thestuffing box 6 is, as shown in FIG. 5( a) or FIG. 6( a), equipped withthe gland packings in such a manner that the gland packings arealternately oriented and where they are thereafter, as shown in FIG. 5(b) or FIG. 6( b), tightened by the packing holder 8, the gland packingsare, like the change from FIG.4( a) to FIG. 4( b), extended and deformedin the directions of the inner and outer diameters as if an umbrellawere spread (so-called washer deformation of conical plate shape), sothat the efficient and excellent sealability is displayed. In addition,the load necessary for extending and deforming the present inventiongland packing from FIG. 4( a) of the shape before tightening to FIG. 4(b) of the shape after tightening is fairly decreased in comparison witha gland packing having a rectangular cross section as conventionallygenerally commonly used. Furthermore, the present invention glandpacking also has no problems such as permeation leakage of the packingitself as occurs to such as a low-density gland packing, and can alsodisplay the sealability sufficiently.

In detail, when the pressure is applied to the present invention glandpacking from a portion giving the load (e.g. a tightening face 8 a ofthe packing holder), the gland packing is compressed in the thicknessdirection as a whole. As to the deformation of the shape due to thiscompression, the presence of the aforementioned angle α and angle β isone factor for enabling easy deformation and extension in the directionsof the inner and outer diameters. Furthermore, because of thedeformation and extension due to this compression, in the gland packingas shown in FIG. 4( b), the peak stress in the directions of the innerand outer diameters is efficiently transmitted greatly particularly atthe following portions of: from the inner-diameter-side angle portion 3c to the stem side; and from the outer-diameter-side angle portion 4 cto the inner wall surface side of the stuffing box, wherein the angleportion 4 c has an opposite-angle relation to the angle portion 3 cconcerning the cross sectional shape. In the present invention glandpacking, this portion which can efficiently transmit the stress ishereinafter referred to as a stress-concentrated point for the sake ofconvenience.

As to the present invention gland packing, for example, in the casewhere the present invention gland packing seals such as the stem or theinner wall surface of the stuffing box, the sealability is displayed bythe peak stress as caused at the stress-concentrated point when thegland packing is extended and deformed in the directions of the innerand outer diameters. Therefore, even if the total stress as transmittedin the directions of the inner and outer diameters (for example, thetotal force that holds the stem) is smaller than that in use of aconventional gland packing, the lowering of the sealability is notobserved. In short, even if the tightening face pressure is smaller thanconventional, the seal can be carried out sufficiently. Therefore, theaxis resistance as caused when the tightening and sealing are carriedout is lowered as the reflective effect. For example, when the glandpacking is used for a seal portion of a valve, the hand torque necessaryfor opening and shutting the valve can be lowered. Similarly, thedeterioration of such as the stem and packing and the deterioration ofthe gland packing itself due to friction when the tightening and sealingare carried out can be lowered greatly. Therefore, it can be said thatthe gland packing is particularly favorable to a seal portion of anequipment in which the axis movement is carried out so frequently as tousually make such as the seal abrasion very large.

When the present invention gland packing displays not less efficient andnot less excellent sealability than conventional ones, even a tighteningface pressure lower than conventional is permitted. Therefore, forexample, there is no especial limitation on such as the packing holder8. These neighboring machines can be prevented from enlarging andweighting, and can be compacted, and besides the entire sealingapparatus can be prevented from enlarging, and can be compacted.

In a specific use in which the high sealability is requested, it hashitherto been determined that the use is met by a gland packing of whichthe size is strictly set for the outer diameter of a stem and the innermeasurements of a stuffing box (gland packing in which: there littleexists so-called tolerance, and there is little opening between thegland packing and the stem, and between the gland packing and the innerwall surface of the stuffing box). However, as mentioned above, thepresent invention gland packing has efficient and soft deformability andextensibility in the directions of the inner and outer diameters, andhas the flat portions that can contact with each other certainly andstably. Therefore, even if the measurements are not strictly setaccording to an object in a specific use, the gland packing can meet theuse. Furthermore, also in cases of usual use, a gland packing having oneset of measurements can meet wide conditions of measurements(measurements conditions of various objects) alone. Therefore, thesetting of the size kinds of the gland packings (kinds of product sizes)may be little, and the production efficiency rises, and the productioncosts can be decreased. Specifically, when the present invention glandpacking is used for a sealing apparatus comprising such as a stuffingbox, the optimum deformation and extension amount to meet the individualconditions of the various objects can be given to the aforementionedgland packing by adjusting the tightening face pressure. Therefore, itcan be used under wide conditions, and simultaneously the highsealability can be achieved. In addition, when a conventional glandpacking is equipped to such as a stem in a stuffing box, it accompaniesdifficulty of equipment in some extent (especially in cases ofhigh-density-type sealing apparatuses or in cases where the highsealability as mentioned above is requested, the difficulty is larger,for example, because such as measurements are considerably strict).However, when the present invention gland packing is used, the highsealability is ensured due to the efficient deformability andextensibility in the directions of the inner and outer diameters,therefore the measurements can afford to be set to make the equipmenteasier than conventional products. Furthermore, even in cases wherevarious changes in size have occurred later, for example, in cases wherethe size of the gland packing has changed from the original size due tosuch as friction and corrosion with the passage of time and in caseswhere the size of the stem or inner wall surface of the stuffing box haschanged from the original size due to such as abrasion and corrosion(although there is no especial limitation to these cases), suitableadjustment of the tightening face pressure makes it also possible thatthe gland packing is extended and deformed efficiently and softly in thedirections of the inner and outer diameters, thereby fitting the sizeagain. Therefore, the optimum sealability can be ensured again.

There is no especial limitation on the density (hardness) of the presentinvention gland packing, but it may be fitly be adjusted to the optimumdensity according to the sealability as requested and peripheralapparatuses. As mentioned above, the present invention gland packing hasefficient deformability and extensibility in the directions of the innerand outer diameters. Therefore, for example, the good deformation andextension in the directions of the inner and outer diameters can becarried out by a tightening face pressure smaller than the tighteningface pressure that has hitherto been regarded as necessary when thedensity is increased higher than usual. Accordingly, the use of thepresent invention gland packing can solve the demerits coming intoquestion about such as conventional gland packings that have higherdensity than usual, especially, rectangular high-density gland packingswherein the above demerits are for example as follows: the lack oftransmitting the stress against the tightening face pressure due to lackof softness (deformability and extensibility) in the directions of theinner and outer diameters; the difficulty of the equipment; theenlargement of apparatuses in compliance with such as dynamic request;and the increase of the axis resistance as caused by the non-uniformdeformation. By such reasons, when the present invention gland packingis molded in high density, various excellent functions (e.g. shapestability, abrasion resistance, anticorrosion, function of receiving ashaft such as a stem (function of preventing a moving error or vibrationof the shaft), and easiness of equipment) can be given to the presentinvention gland packing, though the functions are not limited to these.

There is no especial limitation on the structural shape and materialquality of the present invention gland packing, but specifically,preferred examples thereof include knitted and plaited packings,laminated packings, metal packings, graphite packings, and resin-moldedpackings.

The aforementioned knitted and plaited packings are generally packingsas obtained by knitting and plaiting either one yarn comprised ofvarious fibrous materials (e.g. carbon fibers and aramide fibers), or athread obtained by twisting at least two yarns, into desired shapes bysuch as braiding, braiding-over-braiding, square-braiding, andinterbraiding.

The aforementioned laminated packings are generally packings as obtainedby: stamping out a sheet material; and then processing the resultantmaterial into a desired shape by suitable methods such as cutting; andthen press-molding the processed material with such as a mold.

The aforementioned metal packings are mainly packings as obtained bycompression-molding such as metal foils.

Among these, the graphite packings and fluororesins are particularlyfavorable as the material quality as used in the present invention glandpacking, because they are excellent in chemical resistance andself-lubricity.

The aforementioned graphite packings are generally packings of which themajor material is expanded graphite. Specifically, although notespecially limited, preferred examples thereof include tape-molding-type(curling-type) packings, tape-molding-type packings containing wiremesh, tape-molding-type packings containing metal foil, braided-typepackings, laminated-type packings, and compressed-molding-type packings.The main raw material of the graphite packings is the expanded graphite,but supplement materials (e.g. metal foils, metal wires, metal nonwovenfabrics, various fibrous materials, liquid lubricants, and solidlubricants) can favorably be used further. These may be used eitheralone respectively or in combinations with each other.

The fluororesin packings are packings of which the major raw material isa fluororesin. Specifically, although not especially limited, preferredexamples of the raw material include PTFE (polytetrafluoroethylene), PFA(polytetrafluoroethylene perfluoroalkyl ether copolymers), and FEP(copolymers of tetrafluoroethylene and hexafluoropropylene), and theyare, for example, molded by cutting-processing of sleeve-shaped moldedstructures or by injection molding of raw pellets. The main raw materialis the fluororesin, but supplement materials (e.g. metal foils, metalwires, metal nonwoven fabrics, various fibrous materials, and besides,liquid lubricants and solid lubricants for coating or combining) canfavorably be used further. These may be used either alone respectivelyor in combinations with each other.

There is no especial limitation on the metals as the aforementionedsupplement materials, but preferred examples thereof include aluminum,lead, copper, stainless, Monel, and Inconel. In addition, these may beused either alone respectively or in combinations with each other. Thereis no especial limitation on the shapes when they are used, butpreferred examples thereof include foils, ribbons, particles, and cottonchips.

There is no especial limitation on the fibrous materials as theaforementioned supplement materials, but preferred examples thereofinclude cotton, linen, nylon, PPS fibers, fluororesin fibers,fluororesin fibers containing graphite, carbon fibers, carbonizedfibers, graphitized fibers, metal fibers, glass fibers, aramide fibers,phenol fibers, ceramic fibers, and asbestos. These may be used eitheralone respectively or in combinations with each other.

There is no especial limitation on the liquid lubricants as theaforementioned supplement materials, but preferred examples thereofinclude mineral oils, synthetic oils, fats, synthetic fats, fluorinatedoils, silicone oils, Vaseline, and various greases. These may be usedeither alone respectively or in combinations with each other.

There is no especial limitation on the solid lubricants as theaforementioned supplement materials, but preferred examples thereofinclude graphite, molybdenum disulfide, tungsten disulfide, boronnitride, fluororesins, mica, talc, gold, silver, lead, and various softmetals. These may be used either alone respectively or in combinationswith each other.

There is no especial limitation on alloys and blending resins, butpreferred examples thereof include nylon resins, PPS resins, acetalresins, phenol resins, epoxy resins, and various rubbers. These may beused either alone respectively or in combinations with each other.

In the case where the aforementioned expanded graphite is included as amaterial when the present invention gland packing is molded, there canbe obtained a gland packing that is excellent in performances such aschemical resistance, movability, stress relaxability, and particularly,stability in a wide temperature range, although there is no especiallimitation thereto. In addition, there is no especial limitation on amolding method for the present invention gland packing containing theaforementioned expanded graphite as a material, but, specifically,preferred examples thereof include: 1) a tape-mold molding method whichinvolves curly rolling an expanded graphite tape, and thereafterpress-molding from the direction of a rolling axis; 2) a laminated-sheetmolding method which involves stamping out expanded graphite sheets intoa desired shape with such as a mold, and laminating and press-moldingthese resultant stamped-out sheets; 3) a molding method which involvesknitting and plaiting an expanded graphite yarn, and then press-moldingthe resultant knitted and plaited material; and 4) athree-dimensional-knitting-and-plaiting molding method which involvesmolding into a desired shape with athree-dimensional-knitting-and-plaiting machine. Among these, the 1)tape-mold molding method and 2) laminated-sheet molding method areparticularly favorable.

In the case where the fluororesin such as PTFE or PFA is included as amaterial when the present invention gland packing is molded, there canbe obtained a gland packing that is excellent in performances such aschemical resistance, movability, and low dust generation property,although there is no especial limitation thereto. In addition, there isno especial limitation on a molding method for the present inventiongland packing containing the aforementioned fluororesin, but,specifically, preferred examples thereof include: 1) in case of usingthe PTFE, a molding method which involves cutting-processingsleeve-shaped molded products into a desired shape; and 2) in case ofusing the PFA, a molding method which involves directly shaping rawpellets into a desired shape by such as injection molding.

In addition, as to the molding of the present invention gland packing,there is no especial limitation on a preparing or processing method formaking the aforementioned flat portions, but it may be a preparing orprocessing method as usually used. Specifically, examples thereofinclude methods that involve such as: changing the shape of the mold, asused for molding, in such a manner that the aforementioned flat portionswill be formed; or once molding, and thereafter cutting-processing.

Preferred examples of the sealing apparatus comprising the presentinvention gland packing include a sealing apparatus in which at leasttwo of the aforementioned present invention gland packings are equippedto the stem in stuffing box. In detail, for example, as shown in FIG. 5(a) or FIG. 6( a), it is favorable that the stem 5 in the stuffing box 6is equipped with at least two of the above present invention glandpackings 1 in such a manner that they are piled in alternateorientation, and then the stem 5 and the inner wall surface of thestuffing box 6 is sealed by tightening the packing holder 8. On thisoccasion, the orientation of the shape of the equipped gland packings 1is favorably such that the slopes of the aforementioned other two edges(1 a and 1 b) are alternately oriented. Incidentally, concerning how toalternately orient the slopes, there are, for example, a pattern asshown in FIG. 5( a) and a pattern as shown in FIG. 6( a). In whatorientation and order the equipment is carried out can be changedaccording to the using object and use. In addition, such as the numberof the gland packings as equipped can be variously changed. In addition,it is not limited to the alternating equipment of all the glandpackings, but the equipment can also be carried out in such a mannerthat a part of the gland packings are piled in the same orientation andthe others are piled in alternate orientation. Specifically, unless allthe present invention gland packings are equipped in the same slopeorientation, the effects of the present invention can be displayed inany way of equipment.

Of FIG. 5( a) and FIG. 6( a), either equipping method will do, but theform of FIG. 5( a) is usually favorable in general. If the form of FIG.5( a) is selected, the contact area between both end gland packings andthe stem is in a state of being apart from the pressurizing face of thepacking holder and the inner bottom portion of the stuffing box becauseof the clearance as formed between both end gland packings and thepressurizing face and the inner bottom portion. Therefore, a so-called“protrusion (thrust)” as caused by tightening after the equipment of thegland packings can be prevented, and the lowering of the sealability canbe prevented. The “protrusion (thrust)”, for example, means that, inFIG. 6( a), a portion of the gland packing to which a load is appliedgets into such as: a slight opening of a portion where the stem 5penetrates the inner bottom portion 7 of the stuffing box; or a slightopening between the stem 5 and the packing holder 8. It causes loweringthe sealability of the apparatus.

In the sealing apparatus comprising the present invention gland packing,all the structural factors (e.g. shape, measurements, and further,material quality) of the gland packings 1 as used are favorably the sameas those of each other gland packing in consideration of convenience anduniform sealability regardless of each seal portion. However, there isno especial limitation thereto. Various gland packings, of which such asthe width of the above flat portions, the respective sizes of the aboveangle α and angle β, and the shape or measurements of other portions,and further the material quality are different, may be used in anycombination with each other. Incidentally, as is shown in FIG. 7 andFIG. 8, the inner bottom portion 7 side and/or the packing holder 8 sidein the stuffing box may be equipped with adapter packings 10. Inaddition, as is shown in FIG. 9, at least one of the present inventiongland packings may be used together with at least two ofconventional-type gland packings 10 a of which the cross sectionalshapes are rectangular. In addition, as is shown in FIG. 10 and FIG. 11,the present invention gland packings may be used together withconventional-type gland packings 10 b of which the cross sectionalshapes are rectangular in such a manner that the conventional-type glandpackings are allowed to intervene between the present invention glandpackings. Furthermore, as is shown in FIG. 12, members other than thegland packing may be used together. For example, hard rings 10 bcomprised of such as metals or resins are used with them allowed tointervene, whereby the extent of tightening the entire sealing apparatusor the balance between the sealability and the low torque can beadjusted according to the using object and use. In this way, also whensuch as the adapter packings 10, the above conventional-type glandpackings 10 a, or the hard rings 10 b are used together, all thestructural factors (e.g. shape, measurements, and further, materialquality) of the present invention gland packings 1 are favorably thesame as those of each other gland packing. However, there is no especiallimitation thereto, and the various gland packings as mentioned abovemay be used in any combination with each other. If only gland packingsof a kind are used when such as a stem is sealed, there have hithertobeen many cases such as “requisite performances or items that cannot besatisfied” and “deficient performances that cannot be compensated”.Therefore, for example, at least two kinds of gland packings havingdifferent shapes, densities, and material qualities have been selected,combined, and used. There is no especial limitation on the aboverequisite performances and deficient performances, but, specifically,preferred examples thereof include performance of uniform tighteningdistribution (sealability), heat resistance, pressure resistance, andfrictional resistance.

When a gland packing having a high-density character is, for example,selected as the present invention gland packing, the efficientextensibility and deformability that the present invention gland packinghas can also be displayed in addition to the high-density character.Therefore, the gland packing can be made to have at least both thecharacters of the low density and high density as have hitherto beenthought. Also in the structure of the present invention sealingapparatus, it is favorable in view of simplification.

As is mentioned above, the present invention gland packing has theefficient extensibility and deformability. Therefore, when at least twoof the gland packings are used for the sealing apparatus, the individualgland packings have stress-concentrated points at the inner diameterside and outer diameter side, and the stress can efficiently be causedeven if only one kind of gland packing is used. Moreover, when the glandpacking is allowed to contact with its neighboring gland packings at theflat portions, the stress concentration is raised at the contactportions due to synergistic effect both at the inner diameter side andouter diameter side. Therefore, in the sealing apparatus comprising thepresent invention gland packing, gland packings of a kind are favorablyused also from the viewpoint of simplifying the structure.

In the sealing apparatus comprising the present invention gland packing,as is shown in FIG. 5( a) and FIG. 6( a), a definite space can beprovided between the gland packings 1 as equipped to the stem 5 beforethe packing holder 8 is tightened. The aforementioned space is derivedfrom that: in the cross sectional shape of the gland packing 1, theaforementioned other two edges (1 a and 1 b) have their respectiveslopes of the same orientation as to a vertical axis perpendicular to acentral axis; and the at least two gland packings are equipped in such amanner that the orientations of the above slopes will be alternate. Forthe purpose that the gland packings 1 as equipped to the stem 5 in thestuffing box 6 can, as mentioned above, display the efficientextensibility and deformability in the directions of the inner and outerdiameters, it is favorable that such spatial room is provided.

In the sealing apparatus comprising the present invention gland packing,when the tightening face pressure is applied by the packing holder,then, as is shown in FIG. 5( b) and FIG. 6( b), the gland packings 1utilize the space between them to become extended and deformed whiledecreasing this space. Then, the stress is efficiently andconcentratedly transmitted from the mutually contacting portions of thegland packings, and the stem 5 and the inner wall surface of thestuffing box 6 are sealed. In this case, the tightening face pressure asapplied by the packing holder is efficiently transmitted to the glandpackings 1. Therefore, all the gland packings 1 have stress-concentratedpoints, especially in the above contacting portions. Especially, as isshown in FIG. 5( a) and FIG. 6( a), when all the present invention glandpackings are, as mentioned above, equipped in alternate orientation, thesealing effect as a whole is a multistagewise sealing effect, and theextremely excellent sealability is displayed. In addition, in FIG. 5( a)and FIG. 6( a), all the present invention gland packings are equipped inalternate orientation. Therefore, the above contacting portions, namely,the portions where the flat portions of the present invention glandpackings contact with each other, are extremely excellentstress-concentrated points at both sides of the inner diameter side andouter diameter side, and besides, the high sealability havingsubstantially the same level can be displayed at any stress-concentratedpoint in the stuffing box almost without depending upon the distancefrom the packing holder 8. Usually, when conventional-type glandpackings (e.g. gland packings of which the cross sectional shape isrectangular or quadrangular) were used, it was inevitable that thesealability is lowered as the distance from the packing holder 8 becomesfarther. Therefore, as functions and effects of the present invention,this can be said to be one of particularly excellent effects togetherwith the stress concentration of the above contacting portions.

As is shown in FIGS. 7 to 12, as mentioned above, preferred examples ofthe sealing apparatus comprising the present invention gland packingfurther include: a sealing structure in which adapter packings areequipped at the inner bottom portion 7 side and/or the packing holder 8side in the stuffing box; and a sealing structure including acombination of the present invention gland packing and theconventional-type gland packing of which the cross sectional shape isrectangular.

Specifically, the adapter packing 10 and hard ring 10 b favorably havehigh strength and high elasticity, and they are favorably made of metalsor resins. The adapter packing 10 may be replaced with such as aconventional gland packing of which the cross sectional shape of a ringportion is rectangular, and packings having various material qualitiesmay fitly be selected. In addition, when the adapter packing 10 is usedat the inner bottom portion 7 side and/or the packing holder 8 side inthe stuffing box is favorable in that effects (e.g. preventingprotrusion (thrust) of the gland packing) can be obtained.

In addition, in the sealing apparatus comprising the present inventiongland packing, a gland packing of which the shape is different from thatof the present invention gland packing may fitly be used in combinationtherewith. Examples of the gland packing having such a different shapeinclude the above-mentioned rectangular gland packings, but there is noespecial limitation thereto. In addition, when only the presentinvention gland packings are used as gland packings in the sealingapparatus comprising the present invention gland packing, at leastunless all the present invention gland packings are equipped in such amanner that they are piled in the same orientation, then the effects ofthe present invention can be displayed.

In the sealing apparatus comprising the present invention gland packing,preferred examples of its form include a form in which the equippedgland packings are such that the present invention gland packings andthe rectangular gland packings are alternately equipped in order. Themost favorable examples thereof include a form of the alternatingequipment such that the equipped gland packings are as shown in FIG. 5(a) or FIG. 6( a), namely, a form in which all the equipped glandpackings are equipped in such a manner that the orientations of theslopes of the other two edges of each gland packing are different fromthose of its neighboring gland packing.

The sealing apparatus comprising the present invention gland packing canbe used for what has a sealing portion structure of any type such asso-called standard type or lantern-ring type, although there is noespecial limitation thereto. Furthermore, although not especiallylimited, specifically utilizable examples favorably include: pumps, suchas rotary pumps and reciprocating pumps; valves, such as gate valves andglove valves; and various stirring machines.

While retaining the above-mentioned characters, the present inventiongland packing 1 can favorably be provided with various structuralchanges (changes in shape) as shown below, and can be used for thepresent invention sealing apparatus. In addition, the sealing apparatuscan also favorably be provided with various structural changes (changesin shape). In these, there are also included those which come to havemore excellent characters due to the structural changes.

There is no especial limitation on the above structural changes, but, asto the aforementioned gland packing 1, preferred examples include thosewhich are provided with arch-shaped (arc-shaped) portions as shown inFIGS. 13( a) and (b) when taking note of the edges 1 a and 1 b thatcross the axis 2 b, perpendicular to the central axis 2 a, at angles inthe same direction in the cross sectional shape of the gland packing 1as shown in FIG. 2( a). Similarly, as to the aforementioned sealingapparatus (e.g. stuffing box or packing holder), examples include thosein which a slope is provided to the inner bottom portion 7 of thestuffing box or to a pressurizing face 8 a of the packing holder. As tothese structural changes, all the above portions that are taken note ofmay be either changed or not, and they may fitly be combined. Inaddition, the above structural changes may be applied either alonerespectively or in combinations with each other.

Detailed Description of Preferred Embodiments

Hereinafter, the present invention is more specifically illustrated bythe following examples of some preferred embodiments. However, thepresent invention is not limited to these examples. Incidentally,hereinafter, the unit “part(s) by weight” may simply be referred to as“part(s)” for the sake of convenience.

EXAMPLE 1

As a major raw material, an expanded graphite tape was prepared byslitting an expanded graphite sheet into strips having a width of 15 mm,and this tape was curly rolled. Thereafter, the resultant rolledmaterial was compression-molded with a mold, thus obtaining a graphitegland packing of Example 1 (packing inner diameter: 20 mm, packing outerdiameter: 33 mm, outer-diameter-side thickness: 6.5 mm, angles α and βas shown in FIG. 2( a) or (b): 5° and 5° respectively, width A: 0.15 t,width B: 0.15 t, and density: 1.70 g/cm³) (hereinafter, referred to as agland packing (1)). Herein, the above “outer-diameter-side thickness”means the length of the edge 1 d as shown in FIG. 2( a) or (b).

Four rings of these gland packings (1) were equipped to a sealingapparatus as shown in FIG. 16 (hereinafter, referred to as asealability-testing apparatus), and then the sealability was evaluated.

The sealability-testing apparatus comprises: an upper receptacle havingsuch as a stem (driving shaft) 15, a stuffing box 6, and a packingholder 8; and a lower receptacle that is incorporated with this upperreceptacle by tightening bolts 12 through an O-ring 11. The lowerreceptacle is provided with the following: a pressurizing opening 13 inorder to inject nitrogen gas; a gas-enclosing portion 16; and bearings14 and thrust bearings 17 in order to rotate the stem (driving shaft)15. The gland packings (4 rings) as used for the sealability test areequipped between the inner bottom portion 7 side of the stuffing box andthe pressurizing face 8 a of the packing holder. Then, the inner wallsurface of the stuffing box 6 and the surface of the stem (drivingshaft) 15 are sealed by tightening the packing holder 8. Incidentally,the gland packings (1) were equipped in a pattern having the orientationas shown in FIG. 5( a) and FIG. 16.

When the sealability test is carried out, nitrogen gas was used as afluid that was sealed in the gas-enclosing portion 16 in thesealability-testing apparatus, and that was an object of sealing. Thenitrogen gas is injected from the pressurizing opening 13 into thegas-enclosing portion 16 so that the gas pressure will be constantly 10MPa. While this gas pressure is maintained, the entiresealability-testing apparatus was immersed into water. The tighteningface pressure of the packing holder 8 was stepwise increased 5 MPa by 5MPa from 0 MPa to 45 MPa, and the sealability was tested every step inturn. The judgment of whether the sealability was achieved or not wasmade on the basis of the leaking rate of the nitrogen gas in water. Whenthis value was less than 5.0×10⁻⁵ Pa·m³/s was regarded as when thesealing was achieved. The “tightening face pressure” under which thesealing of nitrogen gas was achieved in this way was recorded to measurethe “strain ratio” and “axis resistance per contact area”. The resultsare shown in Table 1. Incidentally, the leakage of the nitrogen gas wasnot observed at all except in the stuffing box 6. As to the measurementof the aforementioned leaking rate, the leaked nitrogen gas is recoveredby replacement above the water (about 3 minutes), and the leaking rateis calculated from the recovered volume and the recovering time.

In addition, the measurement methods of the tightening face pressure,strain ratio, and axis resistance per contact area are shown below.

Tightening face pressure (MPa):

This is a tightening load per projective (unit) area of the glandpacking as viewed in the direction of the central axis when theaforementioned sealing of nitrogen gas is achieved.

Strain ratio (%):

This is a ratio at which the equipping length of the gland packings inthe direction of the axis (length of from the pressurizing face of thepacking holder to the inner bottom portion of the stuffing box)decreases from before tightening till the aforementioned sealing ofnitrogen gas is achieved after tightening. Specifically, when theequipping lengths of the gland packings in the direction of the axisbefore and after the tightening are regarded as L and l respectively,then the strain ratio (%) can be calculated from the following equation:“strain ratio (%)=(L−1)/L×100”.

Axis resistance per contact area (N/mm²):

This is a value obtained in the following way: the axis resistance(namely, force (load) necessary for rotating the axis) under which theaforementioned sealing of nitrogen gas is achieved is measured by atorque wrench, and the resultant measured value is divided by theapparent contact area that is obtained by multiplying the equippinglength 1 after the tightening of the gland packing by the axiscircumference.

EXAMPLES 2 to 4

Graphite gland packings of Examples 2 to 4 (hereinafter, referred to asgland packings (2) to (4)) were obtained by repeating the sameprocedures as of Example 1 except that the angles α and β and the widthsA and B, as adjusted in Example 1, were changed as shown in Table 1. Inaddition, the same evaluations of the sealability as of Example 1 werecarried out. The results are shown in Table 1.

Comparative Example 1

A graphite gland packing of Comparative Example 1 (of which the crosssectional shape is rectangular) (hereinafter, referred to as comparativegland packing (1)) was obtained by repeating the same procedure as ofExample 1 except that the angle α, the angle β, and theouter-diameter-side thickness (similarly, also inner-diameter-sidethickness) were changed to 0°, 0°, and 6.5 mm respectively. In addition,the same evaluation of the sealability as of Example 1 was carried out.The results are shown in Table 1.

TABLE 1 Com- parative Example 1 Example 2 Example 3 Example 4 Example 1α 5 10 20 30 0 β 5 10 30 20 0 α–β 0 0 −10 10 0 A/t 0.15 0.15 0.15 0.15 —B/t 0.15 0.15 0.15 0.15 — Density of 1.70 1.70 1.70 1.70 1.70 packing(g/cm³) Tightening 25 20 15 20 35 face pressure (MPa) Strain 2 20 30 3217 ratio (%) Axis 1.62 0.87 0.80 1.39 2.34 resistance per contact area(N/mm²)

From the results as shown in Table 1, it is understood that: in any ofcases where the present invention gland packings of Examples 1 to 4 areused, gas can be sealed under a lower tightening face pressure than thatof the conventional rectangular gland packing of Comparative Example 1.Therefore, the present invention gland packings of Examples 1 to 4 canbe applied safely and can display sufficient sealability, even in aportion to which a very high load cannot be applied. In this way, evenif the tightening face pressure is low, the present invention glandpacking can achieve sufficient sealing, and it is understood that theaxis resistance can also be lowered as a result accompanying this.Accordingly, when the present invention glad packing is applied to suchas a valve, the hand torque necessary for opening or shutting it isgreatly decreased. Above all, it is favorable to usually use the presentinvention gland packing for portions where the axis is said to usuallybe moved so frequently that apparatuses and gland packings areremarkably deteriorated by seal abrasion. Similarly, because a lowtightening face pressure is enough, it can be said that: the equipmentand tightening are easily carried out, and no large power is necessaryeven for retaining the tightened state, and the handling property isvery excellent. In addition, the compactness of the entire sealingapparatus can also be achieved.

In this way, the following simulation was carried out in order todirectly explain, from an aspect of the functional mechanism, that suchas the sealability of the present invention gland packing is remarkablysuperior to that of the conventional gland packing (of which the crosssectional shape is rectangular).

That is to say, modeled as to the gland packing (3) and the comparativegland packing (1) were sealing apparatuses comprising 4 rings in totaleach of both gland packings in the form as shown in FIG. 5( a), and thetransmitted face pressures (MPa) to the inner-diameter-side andouter-diameter-side seal faces were determined by the following detailedsimulations. Herein, simulated as to the gland packing (3) was a casewhere sealing was carried out under a tightening face pressure of 20MPa, and simulated as to the comparative gland packing (1) were caseswhere sealing was carried out under tightening face pressures of 20 MPaand 45 MPa respectively.

When the above simulations were carried out, the transmitted facepressures to the inner-diameter-side and outer-diameter-side seal faceswere determined by finite-element analysis (FEA) in a state where thegland packings ware equipped to the sealing apparatus and tightened,wherein the transmitted face pressures were caused by the tighteningface pressure. The method of axis-symmetrical elasticity calculation wasapplied to the finite-element analysis (FEA), and then portions otherthan the gland packing (e.g. the axis, stuffing box, and packing holder)were made of rigid bodies. There were a coefficient of friction, Young'smodulus, Poisson's ratio, density, and number of elements as materialconstants of the gland packing. These values were set by makingreference to such as a strain ratio, righting ratio, and change ofmeasurements per one ring of the gland packing, and values inliterature. Specifically, the coefficient of friction, Young's modulus,Poisson's ratio, and density were set at 0.3, 117.68 MPa, 0.3, and 1.70g/cm³ respectively. The number of elements was set at 400 relative tothe entire gland packings (4 rings) as equipped.

Next, the “length distance” from the pressurizing face of the packingholder to the inner bottom portion of the stuffing box when the packingholder was tightened was regarded as “1”, and then graphs were preparedas shown in FIGS. 14 and 15, in which the X axis is a length distancefrom the pressurizing face of the packing holder, and in which the Yaxis is a “transmitted face pressure (MPa)” corresponding to this lengthdistance. Incidentally, the transmitted face pressure from the outerdiameter side of the gland packing to the inner wall surface of thestuffing box is shown in FIG. 14, and the transmitted face pressure fromthe inner diameter side to the axis (stem) surface is shown in FIG. 15.

From the results as shown in FIGS. 14 and 15, the following isunderstood. Specifically, the present invention gland packing has astress-concentrated point where the tightening face pressure is highefficiently transmitted to both seal faces that are located at the innerand outer diameter sides. Therefore, when this gland packing is used fora sealing apparatus, there exist, for a definite tightening facepressure, at least two acutely peaking seal portions (seal portionshaving a large transmitted face pressure) which are superior whencompared with cases where conventional-type gland packings (of which thecross sectional shapes are rectangular) are used. In addition, the peaksizes are on nearly the same level in any comparison of between theinner-diameter-side peaks, between the outer-diameter-side peaks, andbetween the inner-diameter-side peak and the outer-diameter-side peak,and stable peak values are shown irrespective of the distance from thetightening face or whether at the inner diameter side or at the outerdiameter side. Accordingly, the efficient and multistagewise sealingsynergistic effect can be displayed, and therefrom it is found thatthere is brought not only the excellent sealability as displayed at eachpeak portion, but also as a whole, sealing effects which are much moreefficient and excellent than conventional.

INDUSTRIAL APPLICATION

The present invention can provide a novel gland packing and a sealingapparatus comprising this, wherein the gland packing displays high andstable sealability for a stem and an inner wall surface of a stuffingbox even for uses further requesting the movability (rotation andreciprocating movement), and further, gives excellent effects, such asdecrease of moving resistance of a stem, shape stability, adaptabilityto a corroded and worn-out stem and stuffing box, function for receivingshafts, easiness of equipment, simplification of sealing structure, andcompactness of a sealing apparatus.

1. A gland packing for a stuffing box, comprising a ring packingselected from the group consisting of knitted and plaited packings,laminated packings, graphite packings, and resin-molded packings andwhich can be elastically deformed by compression and has a quadrilateralcross sectional shape with inner and outer diameter sides and first andsecond sides extending between said inner and outer diameter sides,wherein said inner and outer diameter sides of the quadrilateral areparallel to a central axis of the gland packing, and wherein said firstand second sides have slopes of the same orientation with respect to anaxis perpendicular to the central axis, wherein: saidinner-diameter-side has an acute angle portion and saidouter-diameter-side has an acute angle portion of the quadrilateralbeing flat portions; and the slope angles of the first and second sidesare less than 40° with respect to a plane perpendicular to the centralaxis.
 2. A sealing apparatus, which is equipped with a plurality ofgland packings that are piled in a stuffing box, and which seals thestuffing box, wherein: each of the gland packings is a gland packinghaving flat portions arranged at an inner-diameter-side acute angleportion and an outer-diameter-side acute angle portion of a ringpacking, said gland packings being selected from the group consisting ofknitted and plaited packings, laminated packings, graphite packings, andresin-molded packings and which can be elastically deformed bycompression and has a quadrilateral cross sectional shape including:inner and outer diameter sides wherein said inner and outer diametersides are parallel to a central axis of the gland packing; and first andsecond sides extending between said inner and outer diameter sides whichhave slopes of the same orientation with respect to a vertical axisperpendicular to the central axis; the slope angles of said first andsecond sides are less than 40° with respect to a plane perpendicular tothe central axis; and at least one of the gland packings in the stuffingbox is positioned therein in such a manner that the orientations of theslopes of the first and second sides of the at least one of the glandpackings are different from the orientations of the slopes of the firstand second sides of an adjacent gland packing.
 3. A sealing apparatusaccording to claim 2, wherein all the gland packings in the stuffing boxare positioned therein in such a manner that the orientations of theslopes of said first and second sides of each gland packing aredifferent from those of its adjacent gland packing.
 4. A sealingapparatus according to claim 2, which is further equipped with anadapter packing at an inner bottom portion side and/or a packing holderside in the stuffing box.
 5. A sealing apparatus according to claim 3,which is further equipped with an adapter packing at an inner bottomportion side and/or a packing holder side in the stuffing box.
 6. Agland packing, comprising a ring packing having an annular shapeselected from the group consisting of knitted and plaited packings,laminated packings, graphite packings, and resin-molded packings andwhich can be elastically deformed by compression and where said glandpacking has a quadrilateral cross sectional shape with inner and outerdiameter sides and first and second sides extending between said innerand outer diameter sides, said inner and outer diameter sides beingparallel to a central axis of the gland packing; said first side havinga first sloped surface at a first angle with respect to a planeperpendicular to the central axis; said second side having a secondsloped surface at a second angle with respect to the plane perpendicularto the central axis, wherein said first angle is different from saidsecond angle and where said first and second angles are less than 40°with respect to a plane perpendicular to the central axis.
 7. The glandpacking of claim 6, wherein said first angle is less than said secondangle.
 8. The gland packing of claim 6, wherein said first angle isgreater than said second angle.
 9. The gland packing of claim 6, whereinsaid first side includes a first flat surface being substantiallyperpendicular to said inner diameter side and extending between saidinner diameter side and said first sloped surface; and where said secondside includes a second flat surface being substantially perpendicular tosaid outer diameter side and extending between said outer diameter sideand said second sloped surface.
 10. The gland packing of claim 6,wherein said first sloped surface of said first side intersects withsaid outer diameter side to define a first outer edge, and said secondsloped surface of said second side intersects with said inner diameterside to define a first inner edge.
 11. The gland packing of claim 10,wherein said first side has a first flat surface and said first outeredge is spaced from said first flat surface a first distance and wheresaid first inner edge is spaced from said first flat surface a seconddistance that is greater than said first distance.
 12. A sealingapparatus comprising a plurality of stacked gland packings in a stuffingbox for sealing said stuffing box, wherein each of said gland packingscomprises a ring packing having an annular shape selected from the groupconsisting of knitted and plaited packings, laminated packings, graphitepackings, and resin-molded packings and which can be elasticallydeformed by compression and where said gland packing has a quadrilateralcross sectional shape with inner and outer diameter sides and first andsecond sides extending between said inner and outer diameter sides, saidinner and outer diameter sides being parallel to a central axis of thegland packing; said first side having a first sloped surface at a firstangle with respect to a plane perpendicular to the central axis; saidsecond side having a second sloped surface at a second angle withrespect to the plane perpendicular to the central axis, wherein saidfirst angle is different from said second angle and where said first andsecond angles are less than 40° with respect to a plane perpendicular tothe central axis.
 13. The gland packing of claim 12, wherein said firstangle is less than said second angle.
 14. The gland packing of claim 12,wherein said first angle is greater than said second angle.
 15. Thegland packing of claim 12, wherein said first side includes a first flatsurface being substantially perpendicular to said inner diameter sideand extending between said inner diameter side and said first slopedsurface; and where said second side includes a second flat surface beingsubstantially perpendicular to said outer diameter side and extendingbetween said outer diameter side and said second sloped surface.
 16. Thegland packing of claim 12, wherein said first sloped surface of saidfirst side intersects with said outer diameter side to define a firstouter edge, and said second sloped surface of said second sideintersects with said inner diameter side to define a first inner edge.17. The gland packing of claim 16, wherein said first side has a firstflat surface and said first outer edge is spaced from said first flatsurface a first distance and where said first inner edge is spaced fromsaid first flat surface a second distance that is greater than saidfirst distance.